High frequency telegraph transmitter



HIGH FREQUENCY TELEGRAPH TRANSMITTER Filed March 18, 1932 Patented June25, 1935 UNITED STATES HIGH FREQUENGY TELEGRAPH TRANSMETTER ErnstKramer, Eerlin-Tempelhof, and Erich Liittclier, fierlin-Fiiedrichsfelde,Germany, as-

signors to C. Lorenz Aktiengesellschaft, Berlin-Tempelhof, Germany, acompany of Germany Application March 18,

1932, Serial No. 599,738

In Germany March 31, 1931 2 Claims.

In the telegraphic keying of wireless transmitters, the signal impulsestransmitted are rectangular in form since they are formed simply asinterruptions oi the carrier frequency. The rec-- tangular form of thesignals, however, gives rise to a large number of harmonic oscillationswhich easily interfere with other transmitters.

Therefore, in transmitters controlled from a separate oscillator,arrangements have been provided in the grid or anode circuits of thetransmitter proper which prevent a rapid increase in the signal currentsand ensure that signals fade but slowly to zero. This working may becalled rounded wave keying. In these arrangements, the controllingoscillator remains permanently in operation, only the transmitter properbeing keyed. The disadvantage of these arrangements, however, lies inthe fact that duplex working is not possible, since the continuousoperation of the associated controlling oscillator impairs the receptionof the signals from the distant station.

This difiiculty is overcome according to the present invention, bybringing the controlling oscillator into operation only when signals areto be transmitted. However, care must be taken that the transmitter isnot connected until the controlling oscillator is oscillating at itscorrect frequency and that it is disconnected again before thecontrolling oscillator ceases to function. To this end, according to theinvention, a switching arrangement operated by the keying device isprovided.

In Figures 1 and 2, two forms of circuit arrangement which may beemployed are illustrated, but the invention is not limited to thisconstruction. In Fig. 1, St. represents the valve of the controllingoscillator and H the transmitter valve proper. Keying of the controllingoscillator is effected through contact T2 of the relay R2 and contact1'12 of the relay RI, whilst the transmitter is controlled through thecontact N3 of the relay RI. When keying the transmitter the followingoperations take place: As soon as the key T is closed the relay RIresponds and closes contacts rl l, 112 and M3. The relay is so adjustedthat its contact rli closes before its contacts 1'] I and 113. Thecontact 112 closes the grid circuit of the controlling oscillator St. sothat this valve operates and settles into oscillations of its normaloperating frequency. A short time later the main transmitter is keyed bythe contact H3 through an arrangement D in the grid circuit. The closureof contact 1-H of relay RI completes an operating circuit for relay R2.This operating circuit includes the key T. A condenser CR is connectedin parallel with the relay R2. This relay now operates its contact r2which is connected in parallel with the contact 1'12.

The arrangement of inductances and condens- 5 ers D, which is connectedin the grid circuit of the transmitter proper, ensures a slow rise ofthe voltage in the grid circuit and prevents a sudden fall of thevoltage on switching off (rounded wave keying). Such an arrangement mayalso be provided in the anode circuit thereof. At the same time, thearrangement makes its possible for the controlling oscillator to attainits correct operating condition before the transmitter proper radiatesits full energy.

On opening the key T the relay RI falls off first and switches off thetransmitter through the contact M3. The controlling oscillator is notaffected by the opening of the contact r82, since the grid circuit isstill closed through the contact T2 of the relay R2. Although thecircuit for the relay R2 is simultaneously broken by the contact rlLthis relay only falls off after a given time since the condenser OR isconnected in parallel with it. The controlling oscillator is then alsoswitched off by the contact r2 whenthis opens.

A similar arrangement for keying the transmitter is illustrated in Fig.2. In this arrangement, the transmitter is keyed by a reversing key. Inthe position of rest of the key T, the relay R2 is energized and thecontact r2, which is used for connecting the controlling oscillator, isopen.

.When the key T is operated, the circuit for the relay R2 is firstbroken at the left-hand contact of the key T and the controllingoscillator insorted through the contact r2. On fully depressing the keyT, the relay RI is energized andv switches in the transmitter throughthe contact ri. On opening the key T the same operation takes place inthe reverse order. First of all, the circuit for the relay R! is brokenand the transmitter switched off by the contact TI and then the relay R2is inserted and the controlling oscillator put out of operation by thecontact r2.

According to the present invention, it is there fore possible to carryout satisfactory duplex Working and at the same time to employ signalsof rounded form so that harmonics and consequent interferences withother transmitters is avoided to the greatest possible extent.

Modifications may be made within the scope indicated by the appendedclaims, without departing from the spirit or sacrificing any of theadvantages of this invention. For instance, the arrangement D, whichserves to retard the rise and fall of the signal current to its markingand spacing values, may be connected to the valve H in another way thanshown. a

What is claimed is: 1. In a high frequency telegraph transmitter, thecombination of a transmitter circuit with a controlling oscillatorcircuit, a key for producing marking and spacing signals, meansresponsive to each operation of said key to marking positions forswitching on said oscillator before cutting in the transmitter circuitand to each operation of said key to spacing position for switching offthe oscillator after cutting out the transmitter circuit, said meansincluding'relays, and a damping circuit disposed between one of saidrelays and said transmitter circuit.

2. In a high frequency telegraph transmitter, the combination of avacuum tube transmitter circuit with a vacuum tube oscillator circuitfor controlling the transmitter circuit, a key for producing marking andspacing signals, means connested in the grid circuit of said transmitterfor retarding the rise and fall of the signal current to itsmarking andspacing values, and means responsive to each operation of said keywhereby for each marking signal the oscillator circuit is connectedbefore the transmitter circuit is connected and for each spacing signalthe oscillator circuit is disconnected after said transmitter circuit isopened.

ERNST KRAMAR. ERICH LI'JTTCHE

